This application is related in subject matter to co-pending application Ser. No. 09/995,788 entitled xe2x80x9cPurge Valve With Evaluation Port,xe2x80x9d filed on the even date.
The present invention relates to a vapor purge system, and more particularly to a purge system including a valve that provides a reliable measure of flow through the valve.
In a system that is known to Applicants, a valve is used to deliver fuel vapor to an engine intake manifold for use in a combustion process.
In the known system, a fuel tank is in fluid communication with a charcoal canister, such that the charcoal canister receives vaporized fuel from the tank. The collected vapor is delivered from the canister through a delivery port. The valve includes an input and an output, the input being in fluid communication with the delivery port.
The diagnosis and evaluation of flow through the known system is achieved between the delivery port and the inlet port of the valve. In particular, a t-fitting is disposed between the delivery port and the valve. Thus, a direct flow path between the delivery port and the valve is split by the t-fitting, the direct flow path replaced by three flow paths, in particular (1) a flow path from the delivery port to a first arm of the t-fitting, (2) a flow path from the second arm that permits evaluation of the system, and (3) a flow path from the third arm of the t-fitting to the valve for delivery. Diagnosis and testing of the flow diverted through the second arm of the t-fitting is accomplished through a testing member. The flow paths are fuel grade hoses.
A fourth flow path, also in the form of a fuel grade hose, is used to deliver fuel vapor from the valve (i.e., from the valve output) to the engine intake manifold for combustion.
Thus, from the delivery port to the valve output of the known system, four hoses and seven connections are required. The seven connections are as follows: (1) at the vapor delivery port, (2) at the first arm of the t-fitting, (3) at the second arm of the t-fitting, (4) at the third arm of the t-fitting, (5) at the testing member, (6) at the inlet port of the valve, and (7) at the outlet port of the valve.
The known system suffers from a number of disadvantages, in that each hose, connection, and additional, separate component (e.g., the t-fitting) increases the cost and the complexity of the system. Further, each additional connection provides an additional potential leak point within the system. Because vapor can leak from the system between the flow evaluation point and the valve, testing to determine flow through the valve becomes less accurate as the number of leak points increases between the evaluation point and the valve.
The present invention provides a vapor purge system that permits evaluation of the system with a minimum number of hoses and connections, and without the use of additional components. The system includes a valve having first and second ports in communication with a first chamber and a third port in communication with a second chamber, the first and second chambers being defined by a metering member that divides an internal volume of a housing. A diagnostic member having first and second operative states is in communication with the first chamber through the second port. The first operative state prohibits communication with an exterior of the valve, and the second operative state permits communication with the exterior. The diagnostic member provides the ability to reliably measure flow through the valve. The system can use two (2) hoses including three (3) connections from a vapor supply port connected with the first port to the third port operatively connected with a manifold.
The present invention also provides a valve for such a vapor purge system. A housing defines an internal volume. A metering member is disposed in the housing, the metering member dividing the internal volume into first and second chambers. A first port is in fluid communication with the first chamber, the first port adapted to receive fuel vapor. A second port is in fluid communication with the first chamber. A third port is in fluid communication with the second chamber, the third port adapted to deliver fuel vapor for use in a combustion process. A diagnostic member disposed at least partially within the second port and having first and second operative states is in communication with the first chamber. The first operative state prohibits communication with an exterior of the valve, and the second operative state permits communication with the exterior. The diagnostic member provides the ability to reliably measure flow through the valve.
In a preferred embodiment, a vapor supply port is in fluid communication with the first port, and a diagnostic member is in fluid communication with the second port.
The present invention also provides a method of evaluating a vapor purge system having a vapor collection arrangement and a valve that includes a housing defining an internal volume, a metering member disposed in the housing to divide the volume into first and second chambers, a first port in fluid communication with the first chamber, a second port in fluid communication with the first chamber, and a third port in fluid communication with the second chamber. The method includes sealing the first chamber from the second chamber with the metering member, and measuring a flow through the first chamber of the valve.